(TELEGRAPH) — Carbon trading fraudsters may have accounted for up to 90pc of all market activity in some European countries, with criminals pocketing an estimated €5bn (£4.5bn, $7.3bn) mainly in Britain, France, Spain, Denmark and Holland, according to Europol, the European law enforcement agency.

The revelation caused embarrassment for European Union negotiators at the Copenhagen climate change summit yesterday, where they have been pushing for an expansion of their system across the globe to penalise heavy emitters of carbon dioxide.